Method of stabilizing hydrocarbons



Patented July 20, 1948 METHOD OF STABILIZING HYDROGARBONS Richard F. Robey, Cranford, John Fedirko, Elizaboth, and Allan E. Barnett, Westfleld, N. J.,

assignors to Standard Oil Development Company, a corporation oi. Delaware No Drawing.

Application May 26, 1944,

Serial No. 537,540

6 Claims. (Cl. 260-4665) This invention relates to a method of stabilizing hydrocarbon materials and particularly to a method of reducing the peroxide content of hydrocarbons or preventing the formation of peroxides in hydrocarbons which are exposed to air or oxygen.

It is well known that the presence of peroxides in petroleum hydrocarbons of the motor fuel .range tends to induce the formation of gums and to increase the knocking tendencies of motor fuels. Peroxides have also been found to promote deterioration of petroleum lubricating oils, causing bearing corrosion in the absence of oxygen. It is also known that the presence of peroxides is particularly undesirable in hydrocarbons of the diolefin type, since the diolefins tend to polymerize comparatively rapidly in the presence of small quantities of peroxides, whereby rubber-like polymers are formed during storage. The present invention relates particularly to the use of additives which materially inhibit the spontaneous formation of peroxides and which will reduce the peroxide content of hydrocarbon materials when the peroxides are already present. The invention is particularly concerned with the reduction of the peroxide content of diolefins.

Studies of the reactions which butadiene, isoprene, cyclope'ntadiene, the piperylenes, and their higher homologs undergo during storage and the plant processing indicate that there are two types of polymerization which may take place. One type is the dimerization by a Dials-Adler type condensation, which is bimolecular and homogeneous in the liquid phase under a variety of conditions. The second type of polymerization, the formation of plastic materials of high molecular weight, is more serious, since, if such polymerization is permitted to proceed without control, not only will severe losses of valuable material result both in storage and in operations such as distillation, but stoppage of equipment will also. be caused by solid polymer masses. It has been found that this type of polymerization is catalyzed by peroxides. Peroxides of the diolefins may be It has been found, in accordance with the present invention, that the antioxidant compound is rendered more effective and will even reduce the concentration of peroxides at a fairly rapid rate when added to a hydrocarbon already containing such peroxides if a promoter is added which exhibits a standard oxidation potential between itself and its next higher oxidation stage in the range of about --0.'! to 0, measured in volts, the value being the single potential of the electrode when the concentration of ions involved is one molar (unit activity), referring to the hydrogenhydrogen ion couple as zero, the measurements being taken at 25 C.

As illustrative of the eifect of peroxides on the polymerization of diolefins, there will be described an investigation in which the polymerization of isoprene to a viscous liquid of rubber-like polymers was studied to observe the quantitative dependence of polymerization rate upon peroxide concentrations.

EXAMPLEI Measurements were made of the amount of polymerization of pure isoprene at a temperature of 60 C. in the presence of various quantities of the natural peroxide obtained by contacting isoformed by air oxidation,- and the rate of poly-.

merization to plastic substances is related to the peroxide concentration. Certain antioxidants have been found to be quite effective in preventing such peroxide formation, the most useful being the antioxidants of the phenolic type which have aliphatic side chains which render the compounds at least moderately soluble in the hydrocarbons. In some cases the side chain is not required. For example, it has been demonstrated that the presence of hydroquinone practically completely prevents appreciable peroxidation of butadiene by air for a considerable period, and further observations indicate that the same effect is obtained with isoprene.

prene with air. The quantity of peroxide present is indicated by the amount of active oxygen present. The results are shown in Table I.

Peroxide catalyzed polymerization of pure isoprene at 60 C.

Per Cent per Duration Hour to High Polymers 1 P. P. M. Hours 1 Calculated by subtracting rate of dimer formation.

The rate of formation of peroxides by the contact of hydrocarbons with air has been studied.

, The opportunities of higher boiling hydrocarbons coming into contact with air in the process of handling in the plant are particularly great. The fact that the vapor pressures may be less than one atmosphere at ordinary temperature provides on occasion a partial vacuum into which air is easily drawn. The C5 hydrocarbons are known to be excellent solvents for oxygen.

prene when maintained saturated with air at anew ordinary temperatures in a darkened glass vi was determined. Data are given in Table It.

Mean E Rate or permeation of icoprene a air Active Oxy- Time, ms. gen gf million From the data of Example 2 it iaapparent that the per-oxidation is auto-catalytic. i. e., the presence of peroxide catalyzes iurther peroxidation.

EXALIPLE 4 Results 01' the comparison or died: oi teat.- butyl catechol and alpha naphthol on the reduction of tert.-butyl hydroperoxide and isoprene peroxide in aromatic hydrocarbon solution for a.

period oi five hours for each test. with and without promoter, are shown in Table IV.

Tun: IV

Reduction of peroxides Veloci 2 5- Peroxide l Vessel Reductor Promoter lilttl l t, I

one N on; 0.00 80 mhtlz'aa'siai'aaiaiiai: 81%

. None 01!) so Isoprene peroxide .-.ao;.--. 0. 19 one 0.) 110 tort-Duty] bydropcroxide..- Steel.-.- 1.0 do 2.0

1 Initial concentration-100 P. P. M. active oxygen. 1 0.2) wt. per cent concentration in each case. Concentration 0.03 wt. per cent. z( 00/) where c-active oxygen concentration in P. P. M. at time t in hours.

Studies were then made oi the eii'ect of various antioxidants on the rate of polymerization oi isoprene in the presence of added peroxide.

EXAMPLE:

Inhibition of the polymerization of isoprene in the presence 01' natural peroxides was studied at 60 C., using 0.22% alpha naphthol, with and without the presence of methylene blue chloride (0.03%) as a promoter. In all cases the peroxide was present in an amount which provided 100 parts per million of active oxygen. Glass vessels were used. The results are shown in Table 111.

Teen III v I Calculated by subtracting rate of dimer iomxation. P t mmbmo Rate in presence of inhibitor X 100 Rate in absence oi inhibitor With regard to the eii'ect of antioxidants on hydroxy benzenes, as

. and/or sulfur.

It will be noted that tert.-butyl catechol was ineii'ective for reducing the concentration or peroxide during the period of the test, which was live hours, but that'rapid reduction'was caused by adding an activator in the form of methylene blue chloride or stannous chloride. The promoter alone did not cause reduction. Asimilar eiiect was observed with alpha naphthol. 4

The antioxidants which have been found to be I most eiiectively activated by the promoters of the present invention are the phenolic type antioxidants, by whichis to be understood not only phenols and alkylated phenols, but also the polywell as hydroxylated naphthalenes. such as naphthols. Examples ofsuch antioxidants which are particularly useful are the -cresols, vcatechol, hydroquinone, pyrogallol. the

naphthols, and their alkylated derivatives. Since the exact mechanism of the action of the invention is not known, it may find application to other antioxidants such as those containing nitrogen As stated above, the used in conjunction standard oxidation-potential. or about 0.7 to about 0, measured as described above. Examples of promoters 0!. this class which are especially useful in accordance with the present invention are the following, listed with the electrode reacpromoters which have been with the aforesaid phenolic type antioxidantsare compounds exhibiting a 5 tion involved and the corresponding standard oxidation potential:

material containing peroxides in a proportion which tends to cause polymerization of the diole- .Standard Promoter Electrode Reaction Oxidation Potential 'litanous chloride Ti"*+H,0-Ti*++2H++e" 0. 1 Hydrogen sulfide H|S=S+2H++2sr -0. l4 Stanuous chloride. Sl1++=sll 28"--- 0. l5 Cuprous oxide Gu+= Cu 0. l7 Mercurous chloride. 2Hg+2Cl-=Hg|Ch+2e- 0. 27 'Irivalent vanadium salts V+ +H;O-VO '+2H++e-. --0. 81 Uranous salts,. 0. 41 Platinous salts... -0. 4 Suliur -0. 45 Pentavalent molybdenum salt +4H++e- 0. 5 Methylene blue chloride Methylene white=methylene bIue+2H++9e- -0. 53

limited by any of the examples which are set forth above for illustrative purposes only, but is to be limited solely by the terms of the appended claims,

We claim:

1. A diolefln containing dissolved therein a small amount of a phenolic type antioxidant and a small amount of methylene blue chloride.

2. Isoprene containing dissolved therein a small amount of a phenolic type antioxidant and a small amount of methylene blue chloride.

3. A diolefin containing dissolved therein a small amountof tert.-butyl catechol and a small amount of methylene blue chloride.

4. Isoprene containing dissolved therein a small amount of tert.-butyl catechol and a small amount of methylene blue chloride.

5. A composition containing a diolefln and dissolved therein a small amount of tert.-butyl catechol with a small amount of methylene'blue chloride.

6. The method or reducing the peroxide content of a predominantly dioleflnic hydrocarbon ilnic hydrocarbon material, comprising the steps of heating said material in the presence of a small amount of a phenolic type anti-oxidant and a small amount of methylene blue chloride.

RICHARD F. ROBEY. JOHN FEDIRKO. ALLAN E. BARNETT.

REFERENCES crrEo The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,884,431 Watson et al. Oct. 25, 1932 2,006,756 Bartram July 2, 1935 2,023,110 Wilson Dec. 3, 1935 2,031,917 Winning et al. Feb. 25, 1936 2,115,781 Morrell May 3, 1938 2,288,754 Story July 7, 1942 2,361,538 Franz Oct. 31, 1944 2,398,468 Schulze et al Apr. 16. 1

OTHER REFERENCES Cohen: Symposia on Quantitative Biology, vol. 1. -202 (1933).

Lowry et al.: .Jour. Eng. Chem, vol. 27, 413-415 (1935) 

